Pure fluid sensor



United States Patent O 3,363,453 PURE FLUID SENSOR Donald J. Erickson, Minneapolis, Minn., assigner to Honeywell Inc., Minneapolis, Minn., a corporation of Deiaware Continuation-impart of application Ser. No. 352,269,

Mar. 16, 1964. This application Dec. 12, 1966, Ser.

2 Claims. (Cl. 73-54) ABTRACT 0F THE DISCLGSURE A pure fluid device comprising a stationary member having a plane surface containing two pressurel ports which are located in proximity to a body of revolution. Rotation of the body of revolution in a fluid environment results in hydrodynamic pumping which produces a positive pressure at one port and a negative pressure at the other port. The pressure differential produced at the two ports is indicative of the angular velocity of the rotating body or the viscosity or temperature of the working fluid.

This application is a continuation-in-part of my copending application Ser. No. 352,269 filed Mar. 16, 1964, for a Pure Fluid Sensor, now abandoned.

This invention pertains to pure iiuid sensors, and more particularly pure fluid velocity, viscosity or temperature sensors. A pure fluid device is defined for purposes of the application as ya device having absolutely no moving parts other than the lworking medium (fluid).

Since the discovery of pure fluid technology, various control systems have been investigated to determine the applicability of pure fluid thereto. Pure fluid systems are attractive because of .their high reliability and low cost. Pure iiuid systems also possess exceptional environmental tolerance. For example, the operating temperature and radiation tolerance of a pure iiuid device is limited only by the fabrication materials. Pure fluid systems also permit simpler fabrication techniques than those possible with conventional control systems.

The applicant has provided the pure fluid sensor which in one embodiment provides an output signal indicative of the angular velocity of a body of revolution. The output signal may also be indicative of the viscosity o-f a fluid, or the ambient temperature of the sensor. When utilized as a speed sensor, the applicants pure iiuid sensor provides an output signal which is substantially independent of ambient pressure and surface roughness. One particular application of the applicants unique pure iiuid speed sensor is in a pure fluid control system for a turbojet engine, however, it is not limited to this application.

The scope of the applicants invention will become apparent from a study of the accompanying specification and claims in conjunction with the drawings in which:

FIGURE l is a schematic representation of one embodiment of the applicants unique pure fluid sensor;

FIGURE 2 is an enlarged schematic representation of the applicants sensor;

FIGURE 3 is a schematic representation of another embodiment of the applicants sensor; and

FIGURE 4 is a partial cross-section View of the embodiment illustrated in FIGURE 3.

Referring now to FIGURE 1, reference numeral generally depicts the applicants unique pure fluid sensor. A cylindrical housing means 11 is provided having a planar surface 12 on one end thereof. A lirst iiuid passage 13 is provided within means 11. One end of passage 13 intersects wit-h planar surface 12. so as to form a circular orifice 14. A second fluid passage 15 is provided within ICC housing means 11. One end of passage 15 intersects planar surface 12 so as to form a circular orice 16. It will be noted that orice 14 and orifice 16 are spaced apart and are positioned on either side of an axis 1`7 lying in the plane of the surface 12. Orifice 14 and orice 16 are both positioned a distance X from axis 17 (see FIGURE 2).

An output means 20 is also provided. In the particular embodiment of the applicants pure liuid sensor illustrated in FIGURE 1, the output means 20 comprises a difierential pressure sensor which produces an output signal indicative of the differential pressure sensed. The other end of iiuid passage 13 is connected to output means 20 by means of a conduit 21. The other end of fluid passage 15 is connected to output means 2li by means of a fluid conduit 22.

FIGURE 2 is an enlarged schematic representation of the applicants pure Huid sensor illustrated in FIGURE l. Like reference numerals will be utilized in FIGURE 2 to identify the components described with reference to FIGURE 1. Housing means 11, planar surface 12, fluid passage 13, oriiice 14, iiuid passage 15, and orifice 16 are illustrated in FIGURE 2. Housing means 11 has a flange 18 thereon which is rigidly attached to stationary mounting means 19. Mounting means 19 functions to mount housing means 11 such that surface 12 is contiguous to a rotating body of revolution. Reference numeral 25 identities a body 'of revolution (partially broken away) having a radius R. Body 25 is supported by any suitable bearings (not shown) in stationary support 24 and is rotatable about its axis of revolution`23 which is perpendicular to the plane of the drawing of FIGURE 2. Body 25 may be rotated about axis 23 by any suitable means (not shown). The means for rotating body 25 may, for example, be a turbojet engine. It should be noted, however, that it is not necessary for body 2.5 to be separate from the means by which it is rotated. For example, body 25 may be the shaft which carries the turbine and/ or compressor in a turbojet engine. The axis of rotation of body 25 is parallel to axis 17 which lies in the plane of surface 12. A point of minimum clearance lbetween surface 12 and periphery 26 of body 25 is located on axis 17. The minimum clearance between body 25 and planar surface 12 is indicated by reference symbol hi. In one successful embodiment of the applicants unique sensor h equals .0005 inch.

4Upon rotation of body 25 about axis 23 with an angular velocity direction indicated by the arrow identified by reference numeral 29, a hydrodynamic pumping action occurs between sensor 10 and body 25. Theoretical analysis and experimentation has shown that a pressure build up occurs ahead of axis 17 and a vacuum develops vbehind axis 17. A pressure profile is superimposed upon FIGURE 2 and is identified by reference numeral 28. The pressure build up is proportional to the angular velocity w of body 25 and the viscosity of the uid therebetween (for example air). The pressure build up is also a function of the minimum clearance h between planar surface 12 and periphery 26 of body 25 and a |function of the radius R of body 25. This relationship isindicated in the following formula:

radius of body 25, m equals the clearance modulus h/R, and X equals the distance from axis 17 to the pressure and vacuum peaks. 'Ihus orifice 14 and orice 16 are positioned a distance X from axis i7 so as to 0btain la maximum signal output. As the formula indicates, the distance X is a function of the radius of body 2S and the clearance h between body 25 and planar surface 12.

The positive pressure which builds up in passage 13 is indicated by the symbol -l-P in FIGURE 2. The negative pressure developed in passage 15 is identified by reference symbol -P in FXGURE 2. The pressure differential between passages 13 and 15 is conveyed through conduits 2t), 21 respectively to output means 20. As i11- dicated by the formula above, the output differential pressure signal is independent of ambient pressure levels. In addition, the surface roughness of body 2.5 does not effect the boundary layer pressure build up so that the output signal is also independent of surface condition.

As indicated by the formula, a differential pressure output signal is obtained from the applicants unique pure fluid sensor which is indicative of the angular velocity w of body 25. Thus the applicants sensor may be utilized as a pure fluid speed sensor. It is evident from the formula that the differential pressure output signal of the sensor is also indicative of the dynamic viscosity ,a of the fiuid. Therefore, if the parameters of speed, temperature (which effects dynamic viscosity y. and clearance T1), clearance h, and radius R are held constant, the applicants sensor may be utilized to sense liuid viscosity. In addition, if the parameters of speed and R are held constant, the differential pressure output signal is indicative of temperature because of the effect of the temperature upon the viscosity and clearance (if body and housing 11 are lfabricated of materials having different coefficients of expansion).

When the applicants sensor is utilized as ya speed sensor or viscosity sensor and `a range of temperatures is expected it is necessary to negative the effects of temperature upon the differential pressure output signal. This is accomplished by designing the coefficients of expansion of housing means 11 and body 25 to vary the clearance h to compensate for variations in viscosity due to temperature.

In various pure fluid control systems, it is necessary to utilize the signal of the sensor to initiate corrective action. For example, if the sensor is utilized as a device in a speed limiting control loop, the output signal of the speed sensor is utilized -to control the means generating the angular velocity ofthe body. A typical example would be a pure fluid control system for a turbojet engine. FIG- URE 3 illustrates an alternate embodiment of the applicants invention :adapted to perform this function. The sensor is identified by reference numeral 3f). A cylindrical housing means 31 is provided having a planar surface 32 on one end and thereof. An expanding passage 33 is provided Within housing 31, one end of which intersects With planar surface .32 so as to form an elongated orifice 34. The length of orifice 34 is better illustrated With reference to FIGURE 4. An elongated orifice is necessary because of the demands of increased fluid liow when sensor is connected in a pure fiuid control system. The amount of liuid flow available is dependent upon the area of oritice 34. Referring to FIGURE 2, the pressure profile illustrated extends perpendicular to the plane of the drawing as far as the surface 12 and surface 26 extend contiguous one another. Thus, it is clear that by extending the dimension of the orifice in this direction more fiuid flow is obtained. An expanding fiuid passage 35 is also provided within housing 31, one end of passa-ge 35 intersects with planar surface 32 so as to form an elongated orifice 36. It will be noted that orifice 34 and orifice 36 are spaced apart `and positioned on either side of and parallel to a first axis 37. Axis 37 lies in the plane of planar surface 32.

An output means 40 is also provided. Output means tti in this particular embodiment comprises a proportional pure iiuid amplifier. Pure fluid amplifier 40 comprises a supply nozzle 41, a first control passage 42 and a second control passage 43, an interaction chamber 44, a first output leg 45, and a second output leg d6. Passage 33 is connected to control passage 4Z, by means of fluid conduit d'7. Fluid passage 35 is connected to control passage 43 by fluid conduit 48.

Sensor 30 functions in a manner similar to speed sensor it?, and thus the operation thereof need not be described in detail. The shape of orifices 34 and 35 allow `a greater fluid flow therethrough so as to Operate fluid amplifier 40. The differential pressure signal provided by sensor 3ft is applied across control passages 42 and 43 of fluid amplifier et). Thus the output signal of fluid amplifier 40 is indicative of the angular velocity of a body of revolution positioned contiguous with planar surface 32 along axis 37. The output signal is at a higher magnitude, that is it is amplified by fiuid amplifier 4t) and is utilized by the cont-rol system to initiate appropriate control action. This embodiment may be utilized to sense viscosity or temperature also.

Although the invention has been described and illustrated in detail, it is to be clearly understood that the same is by way of illustration and example only and is not to be taken by Way of limitation, the spirit and scope lof this invention being limited only by the terms of the appended claims.

What is claimed is:

l. A pure fluid sensor comprising:

housing means having a planar surface thereon;

said housing means having a first uid passage therein, one end of said first passage intersecting lwith said surface .and forming a first orifice;

said housing means having a second fiuid passage therein, one end of said second fiuid passage intersecting with said surface and forming a second orifice, said rst orifice and said second orifice being spaced apart and positioned on either side of a first axis;

mounting means for mounting said housing means so that said surface is positioned a distance h from the periphery of a body of revolution having a radius R, said body of revolution being rotatable about its axis of revolution, the direction of said first axis being substantially parallel to the direction of said axis of revolution, said first and said second orifices being positioned a distance equal to %hR on either side of said rst axis; and

output means responsive to the dierence in pressure between said first orifice and said second orifice, said output means being operable to provide a signal indicative of the difference in pressure between said first orifice and said second orifice.

2. The pure fiuid sensor of claim 1 wherein:

said first and second orifices are elongated in cross section and are parallel to said first axis; and

said output means is a proportional fluid amplifier means.

References Cited UNITED STATES PATENTS 2,982,902 5/1961 Le Gates et al. 3,111,838 11/1963 Bucalo 73--53 FOREIGN PATENTS 1,160,652 l/l964 Germany.

LOUIS R. PRiNCE, Primary Examiner.

D. O. WOODEL, Assistant Examiner.. 

